1. Field of the Invention
The present invention is directed to an apparatus and method for minimizing a subject's pain perception during a medical procedure and, more specifically, to a modular system for obtaining a blood sample from a subject while minimizing pain perception.
2. Description of the Related Art
Due to the pain often associated with invasive medical procedures, such as blood sampling and the like, many people are reluctant to visit a doctor or to obtain needed diagnostic tests and other beneficial medical procedures. This is particularly true in the case of children, who, if traumatized, may develop a lasting fear of doctors and/or medical procedures that can persist into adolescence or even adulthood. This reluctance is often aggravated in situations where multiple punctures must be made to obtain the necessary quantity of blood or other bodily fluid. In this regard, data published by H. Fruhstorfer, et al. in Practical Diabetes International, Vol. 12, No. 4, July/August 1995, demonstrated that increasing penetration depth provides more blood from a single puncture. Unfortunately, however, increased penetration depth often increases pain perception during the procedure.
Previous attempts to reduce pain perception during invasive procedures include various devices and methods for introducing a local anesthetic, such as Lidocaine.RTM. or ethylchloride, prior to piercing. For example, transdermal electrode patches have been used to drive a local anesthetic by ionic transport into the dermal tissue layer before intravenous line placement. Transcutaneous electrical nerve stimulation (TENS) has also been used to relieve both acute and chronic pain. TENS involves the application of a constant current to the skin for durations ranging from a few minutes to as long as 30 minutes.
Another method and apparatus for reducing pain perception was disclosed by McCann in U.S. Pat. No. 2,258,857. The apparatus includes a vibrating unit having a contacting element adapted to contact a patient's face during a dental procedure. In operation, the patient activates the vibrating unit and holds the unit in place on his face, proximate the ear. The vibrations purportedly distract and confuse the patient's nerve functions, thereby lessening pain perception by preventing the patient's nerve sense from locating the exact point of the pain. Also, the noise produced by the unit purportedly overcomes all noises produced by other instruments during the dental procedure, thereby further distracting the patient from the dental procedure.
A device for reducing pain perception during injections was disclosed by Kravitz in U.S. Pat. No. 3,620,209. The device includes a casing adapted to be pressed against a patient's skin, a strap for securing the casing to the patient, and vibratory means positioned within the casing. In operation, the casing is secured to the patient, and the vibratory means is actuated. After the patient's skin is vibrated sufficiently to stimulate the pain center of the skin, a needle (which does not form part of the device) is injected into the patient, proximate the device, and the pain of the injection is purportedly minimized by the vibration.
Another device for reducing pain perception associated with injections was disclosed by Pokras in U.S. Pat. No. 5,647,851. The device is a portable, hand held vibrating injection device including an injection needle and a housing enclosing a vibrator. In operation, the vibrator vibrates the needle as it penetrates the patient's skin, thereby purportedly lessening the amount of pain and discomfort experienced by the patient. The vibration of the needle also purportedly accelerates migration of the injected medication into the subcutaneous tissue and away from the puncture site.
Various other approaches and apparatus have been proposed to reduce the perception of pain while drawing blood samples, such as those disclosed in U.S. Pat. No. 4,462,405, U.S. Pat. No. 5,035,704 and WO 97/28741.